Photoelectric conversion device and method of driving photoelectric conversion device

Abstract

A photoelectric conversion device includes a plurality of pixels arranged to form a plurality of columns, a plurality of comparison circuits provided corresponding to the plurality of columns and including a first input node to which a pixel signal output from a pixel of a corresponding column is input and a second input node to which a reference signal is input, a plurality of buffer circuits provided between a reference signal line to which the reference signal is supplied and each of the second input nodes of the plurality of comparison circuits, and a first switch circuit configured to set a connection state between output nodes of the plurality of buffer circuits.

What is claimed is: 
     
       1. A photoelectric conversion device comprising:
 a plurality of pixels arranged to form a plurality of columns; 
 a plurality of comparison circuits provided corresponding to the plurality of columns, each of the plurality of comparison circuits including a first input node to which a pixel signal output from a pixel of a corresponding column is input and a second input node to which a reference signal is input; 
 a plurality of buffer circuits provided between a reference signal line to which the reference signal is supplied and each of the second input nodes of the plurality of comparison circuits; and 
 a first switch circuit configured to set a connection state between output nodes of the plurality of buffer circuits. 
 
     
     
       2. The photoelectric conversion device according to  claim 1 ,
 wherein the plurality of buffer circuits includes a first set including a part of the plurality of buffer circuits and a second set including another part of the plurality of buffer circuits, and 
 wherein the first switch circuit includes a first circuit configured to set a connection state between the output nodes of the buffer circuits of the first set and a second circuit configured to set a connection state between the output nodes of the buffer circuits of the second set independently of the first circuit. 
 
     
     
       3. The photoelectric conversion device according to  claim 2 , wherein the buffer circuits of the first set and the buffer circuits of the second set are alternately arranged. 
     
     
       4. The photoelectric conversion device according to  claim 2  further comprising:
 a plurality of output lines provided corresponding to the plurality of columns, each of the plurality of output lines being configured to output the pixel signal from the pixel of the corresponding column; and 
 a second switch circuit configured to set a connection state between the plurality of output lines. 
 
     
     
       5. The photoelectric conversion device according to  claim 4 , wherein the second switch circuit includes a first circuit configured to set a connection state between output lines of columns in which the buffer circuits of the first set are arranged, and a second circuit configured to set a connection state between output lines of columns in which the buffer circuits of the second set are arranged independently of the first circuit. 
     
     
       6. The photoelectric conversion device according to  claim 4  further comprising a first capacitor connected between the output line and the first input node. 
     
     
       7. The photoelectric conversion device according to  claim 1  further comprising a control circuit configured to control the plurality of comparison circuits,
 wherein each of the plurality of comparison circuits includes a reset switch configured to reset a threshold voltage to a voltage corresponding to a potential difference between the first input node and the second input node, and 
 wherein the control circuit is configured to turn on the reset switch during at least a part of a period in which the first switch circuit is turned on. 
 
     
     
       8. The photoelectric conversion device according to  claim 2  further comprising a control circuit configured to control the plurality of comparison circuits,
 wherein each of the plurality of comparison circuits includes a reset switch configured to reset a threshold voltage to a voltage corresponding to a potential difference between the first input node and the second input node, and 
 wherein the control circuit is configured to turn on the reset switch and switch the reset switch from on to off, during a period in which the first circuit of the first switch circuit is on and the second circuit is off. 
 
     
     
       9. The photoelectric conversion device according to  claim 8 , wherein
 the plurality of comparison circuits includes a first set of comparison circuits arranged in the same columns as the buffer circuits of the first set and a second set of comparison circuits arranged in the same columns as the buffer circuits of the second set, and 
 wherein a voltage of the reference signal line is different between a timing at which the reset switch of the comparison circuit of the first set is switched from on to off and a timing at which the reset switch of the comparison circuit of the second set is switched from on to off. 
 
     
     
       10. The photoelectric conversion device according to  claim 1  further comprising:
 a plurality of dummy buffer circuits provided corresponding to the plurality of columns; and 
 a third switch circuit provided between the reference signal line, and the plurality of buffer circuits and the plurality of dummy buffer circuits, 
 wherein the reference signal line includes a first reference signal line configured to supply a first reference signal and a second reference signal line configured to supply a second reference signal, and 
 wherein the third switch circuit is configured to connect the first reference signal line to one of the buffer circuit and the dummy buffer circuit in each of the plurality of columns and connect the second reference signal line to the other of the buffer circuit and the dummy buffer circuit in each of the plurality of columns. 
 
     
     
       11. The photoelectric conversion device according to  claim 1 , wherein the plurality of buffer circuits is provided in parallel between the reference signal line and the plurality of comparison circuits. 
     
     
       12. The photoelectric conversion device according to  claim 1 , wherein the plurality of buffer circuits is provided in series on a path through which the reference signal is supplied. 
     
     
       13. The photoelectric conversion device according to  claim 1  further comprising a second capacitor connected between the buffer circuit and the second input node. 
     
     
       14. The photoelectric conversion device according to  claim 1 , wherein each of the plurality of comparison circuits is configured to compare the pixel signal with the reference signal whose level changes with lapse of time, and to output a comparison signal indicating a different level in a case where a difference between the pixel signal and the reference signal is smaller than a threshold value and a case where the difference between the pixel signal and the reference signal is larger than the threshold value. 
     
     
       15. An imaging system comprising:
 the photoelectric conversion device according to  claim 1 ; and 
 a signal processing device configured to process a signal output from the photoelectric conversion device. 
 
     
     
       16. A movable object comprising:
 the photoelectric conversion device according to  claim 1 ; 
 a distance information acquisition unit configured to acquire distance information to an object from a parallax image based on a signal from the photoelectric conversion device; and 
 a control unit configured to control the movable object based on the distance information. 
 
     
     
       17. Equipment comprising:
 the photoelectric conversion device according to  claim 1 ; and 
 at least one of
 an optical device corresponding to the photoelectric conversion device, 
 a control device configured to control the photoelectric conversion device, 
 a processing device configured to process a signal output from the photoelectric conversion device, 
 a mechanical device that is controlled based on information obtained by the photoelectric conversion device, 
 a display device configured to display information obtained by the photoelectric conversion device, and 
 a storage device configured to store information obtained by the photoelectric conversion device. 
 
 
     
     
       18. A photoelectric conversion device comprising:
 a plurality of pixels arranged to form a plurality of columns; 
 a plurality of comparison circuits provided corresponding to the plurality of columns, each of the plurality of comparison circuit including a first input node to which a pixel signal output from a pixel of a corresponding column is input via a first capacitor and a second input node to which a reference signal is input via a second capacitor; 
 a plurality of buffer circuits provided between the reference signal line to which the reference signal is supplied and each of the second input nodes of the plurality of comparison circuits; 
 a switch circuit configured to switch a connection state between output nodes of the plurality of buffer circuits; and 
 a control circuit configured to control the switch circuit, 
 wherein the comparison circuit is enabled to perform an offset clamp operation of setting an offset based on voltages input to the first input node and the second input node, and 
 wherein the control circuit is configured to connect between the output nodes of the plurality of buffer circuits during at least a part of a period during which the offset clamp operation is performed. 
 
     
     
       19. The photoelectric conversion device according to  claim 18 , wherein the control circuit is configured to disconnect the output nodes of the plurality of buffer circuits after the offset clamp operation ends. 
     
     
       20. A method of driving a photoelectric conversion device including a plurality of pixels arranged to form a plurality of columns, a plurality of comparison circuits provided corresponding to the plurality of columns and including a first input node to which a pixel signal output from a pixel of a corresponding column is input and a second input node to which a reference signal is input, a plurality of buffer circuits provided between a reference signal line to which the reference signal is supplied and each of the second input nodes of the plurality of comparison circuits, and a switch circuit configured to be enabled to switch a connection state between output nodes of the plurality of buffer circuits, the method comprising:
 connecting the output nodes of the plurality of buffer circuits by turning on the switch circuit in a first operation mode; and 
 disconnecting the output nodes of the plurality of buffer circuits by turning off the switch circuit in a second operation mode. 
 
     
     
       21. A method of driving a photoelectric conversion device including a plurality of pixels arranged to form a plurality of columns, a plurality of comparator circuits provided corresponding to the plurality of columns and including a first input node to which a pixel signal output from a pixel of a corresponding column is input, a second input node to which a reference signal is input, and a reset switch configured to reset a threshold voltage to a voltage corresponding to a potential difference between the first input node and the second input node, a plurality of buffer circuits provided between a reference signal line to which the reference signal is supplied and each of the second input nodes of the plurality of comparison circuits, and a switch circuit configured to be enabled to switch a connection state between output nodes of the plurality of buffer circuits, the method comprising:
 connecting the output nodes of the plurality of buffer circuits by turning on the switch circuit; and 
 turning on the switch circuit during at least a part of a period in which the reset switch is turned on. 
 
     
     
       22. The method of driving a photoelectric conversion device according to  claim 21 , wherein the reset switch is turned on during a period in which the switch circuit is turned on.